Terms of the deal, which took place Jan. 15, were not disclosed. A spokeswoman for Memphis, Tennessee-based Helios said that Helios' current leadership and account management teams will remain in place after the acquisition.

A spokesman for Minnetonka, Minnesota-based OptumRX said that Helios will be folded into Optum's existing workers comp and auto no-fault PBM business.

“Helios' proven track record of solving the unique and complex challenges of managing workers' compensation health care expenses supports our continued focus on supporting the evolving needs of our customers and members,” the OptumRX spokesman said in an emailed statement to Business Insurance on Wednesday.

“Working together, Helios will be better positioned to effectively serve the current and future needs of clients by accessing the expertise and breadth of the OptumRx organization and as a result provide more comprehensive solutions and more aggressively manage expenses,” Helios' spokeswoman said in an emailed statement Wednesday. “Leveraging the scale of the organization will also help Helios provide clients with enhanced products and services, including access to broader networks and greater pharmaceutical purchasing power.”

The deal between OptumRX and Helios follows mergers and acquisitions by both firms in the recent past. In July, OptumRX acquired Catamaran Corp. for $12.8 billion, making OptumRX the third-largest PBM based on prescription volume.

Helios was created in August 2014 following the merger of two workers comp PBMs, Progressive Medical Inc. and PMSI Inc.